Electric lamp for projection apparatus



Feb. 12, 1924. A 1,483,449

B. JOHNSON ELECTRIC LAMP FOR PROJECTION APPARATUS Filed Sept. 15. 1921 ATTORNEY Patented F eb. 12, 1924.

NT OFFICE.

BEBNAYS JOHNSON, OI" NEWARK, NEW JERSEY, ASSIGNOR TO WESTINGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC mm'r son rnomc'rron arimrus'.

.Application filed September 151921. Serial 1T0. 500,918.

To all whom it may concern:

Be it known that I, BERNAYS JOHNSON, a citizen of the United States, and a resident of Newark, in the county of Essex and State of N w Jersey, have invented a new and useful Improvement in Electric Lam s for Projection the allowing is a speci cation.

This invention relates to incandescent electric lamps and more particularly to electric lamps forum in projection apparatus.

1 In, projection apparatus used in the exhibition of motion pictures, stereopticom slides, etc., a light source of high intensity is required. This light source must be highly concentrated in order to be effectively utilized .in obtaining a given screen illumination. This is due to the fact that the opening in the aperture plate of the projection machine is small and all light cast upon the screen must be focused to pass therethrough.

In some forms of incandescent lamps now used as light sources, the filament arrangement is of the mono-plane or bi-plane type, and a reflector is required to effect a solid source of light which is focused upon the aperture plate. These lamps are customarily desi ed to consume 600 or 900 watts and are either 30 volt 20'ampere or 30 volt 30 ampere. This voltage being lower than Ahpparatus, of which commercial voltages, necessitates a trans-' former and auxiliary apparatus to permit using the lamp.

If the len of the filament in the mono plane or bi-plane lamp is increased to permit its direct use upon a 110 volt circuit, several sections of the filament extend beyond the opening in the aperture plate, i. e., the width of the filament is greater than the width of the aperture plate opening. Consequently, the light derived from the outer sections is lost for projection purposes.

It is an object of my invention to pro vide such mounting or arrangement of the filament of "an incandescent lamp that a given voltage may be obtained and no appreciable portion of the light produced be lost on account of the filament extending over a iven area.

Anot er object of the invention is the provision of an incandescent lamp having its filament arranged in such manner that, when-viewed in the direction of a projectin axis, the efiect is that of afsolid beam 0 light restricted to a bution.

A further object of the invention is the production of lam s havi their filaments so arranged that t e necessity of reflectors, in obtaining a uniform screen illumination, is materially reduced and in some instances eliminated Other objects of the invention will be apparent from a reading of the following description.

In the drawings which form a part of this specification, s

Fig. 1 is a view, in elevation, of a la partially broken away to show my preferred arrangement of filament;

Fig. 2 is a sectional view taken on line II-II of Fig. 1; and,

given area of distri- Fig. 3 1s a diagrammatic illustration of the arran ement of the filament sections, showing t e effective illuminating portions thereof.

Referring to the drawings and particularly to Fig. 1, a lamp 1 is shown as comprising a filament 2 mounted within a gas-filled envelope 3. The filament 2 comprises a plurality of coiled sections supported in a V formation by wires 4'and 5 and connected to leadingin conductors 6. The length of the filament is determined by the normal voltage at which the lamp is to be operated. For exam le, a lamp of given wattage and voltage ias a longer filament than a 'lamp of the same watta e and lower voltage. My invention rovides for so mounting the several sections that each of them, irrespective of the length of the filament, is effective for projection purposes. These sections may be mounted within the lamp envelope in any desired manner, with the one restriction that the opening of the V formation does not substantially exceed the width of the aperture in the a erture plate of the projection apparatus, i obvious reason that any sections mounted outside the limits ofthe aperture plate opening are of no assistance in illuminating the screen, as the light rays therefrom cannot be focused within this opening.

' I have found that, by arranging-the sections in a V-shape, all of the sections are readily ositioned within the allowable overall widt and that, as the number of sections increase, the depth of the V will increase. Figs. 2 and 3 illustrate the maxior the 

